A step counter or pedometer is a portable carried by a user that provides an estimate of distanced travelled by foot of a user. Pedometers, which are typically electronic or electromechanical device, originally were intended to be worn on a belt are now incorporated into many different types of fitness devices that are worn or carried by users, such as smart phones, watches and bracelets. Conventional pedometers use accelerometers to sense body motion, and based on the body motion count the user's steps. This step count may then be converted into distance using stride length.
One approach for implementing a pedometer may include plotting accelerometer data versus time, and then count a step whenever the accelerometer data exceeds a reference threshold having a predetermined value. While the plot of accelerometer data may have a profile that is similar for each step and may work for certain cases, the approach may result in an inaccurate step count. This is because the accelerometer data pattern varies widely due to a number of factors such as peculiarities in the user's gait, whether the user in a vehicle, and the location of the pedometer relative to the user which may cause erroneous swinging motions, e.g., when worn on a wrist or carried on a backpack.
Today's pedometers may utilize MEMS inertial sensors and sophisticated software to detect steps. These MEMS inertial sensors may have either 1-, 2- or 3-axis detection of acceleration, which permit more accurate detection of steps with fewer false positives. Although there are many software approaches used to analyze the output of the inertial sensor and estimate the step count, typically increased step count accuracy requires increased mathematical calculations. The problem is that these calculations are computationally expensive in terms of both time and processor power and may have an impact on battery life of the device, particularly if the device includes a touchscreen.
Accordingly, what is needed is an improved pedometer function that is capable of filtering out swinging movements and false steps but in a low-power device.